Method of manufacturing rubber



Nov. 8, 1938. T. J. ELLIS 2,135,570

METHOED OF MANUFACTURING RUBBER VALVE STEMS Original Filed D60. 15, 1934 ntor 71 M190 J 18 attorney '4 Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE METHOD OF MANUFACTURING RUBBER VALVE STEMS Tharon J. Ellis, Akron,

Ohio, assignor, by mesne assignments, to The Dill Manufacturing Company; Cleveland, Ohio, a corporation of Ohio 1 Claim.

This invention relates to valve stems for inflatable articles such as inner tubes for pneumatic tires and the like, and more especially it relates to rubber valve stems of the character 5 mentioned that have metal inserts, such as a valve tube molded thereinto.

The chief objects of the invention are to facilitate the manufacture of the valve stems; to prevent the flow of rubber onto normally exposed portions of the inserts, during molding of the valve stem; to obviate the necessity for bumng the vulcanized rubber valve stem to remove overflow rubber from the exposed portion of the insert; and to secure accuracy of construction in the finished product. Other objects will be manifest as the specification proceeds.

This application is a division of my copending application Serial No. 757,660, filed December 15, 1934.

Of the accompanying drawing:

Figure 1 is a fragmentary sectional View through a sectional vulcanizing mold, and the improved valve stem, in section therein;

Figure 2 is a detail view, on a larger scale, of a portion of the mold and work shown in Figure 1; and

Figure 3 is a side elevation of the finished valve stem.

Referring to the drawing, is a rubber valve stem structure that is formed with the usual base flange H to facilitate its incorporation in the wall of an inflatable rubber article, such as an inner tube, and I2 is a tubular metal insert or valve tube that is molded axially into the stem structure and which contains the usual valve mechanism (not shown). The valve tube has one end portion formed exteriorly with a plurality of circumferential grooves I4, I4, this portion of the insert being molded into the stem 40 structure It) whereby the grooves I4 are filled with rubber, thus effecting a mechanical interlock of the metal and rubber to supplement the adhesion therebetween. The opposite end portion of the insert projects from the end of the stem structure and is formed with a male screw thread 15 to receive the usual valve cap (not shown). Intermediate the grooves i l and screw threads l5 the insert is formed with a radially extending circumferential flange l6 having its 50 lateral face nearest the said screw threads slightly beveled or tapered as shown at H. The rubber at the end of the stem structure l0 overlies the peripheral face of flange l6 and is substantially flush with the tapered face I1 thereof.

The improved valve stem is molded and vulcanized in a sectional mold shown most clearly in Figure 1, said mold comprising a base plate 20, an intermediate plate 2|, a cover plate 22, a mandrel and registering pin 23 mounted in said cover plate, and a socket member 24 mounted in said base plate 28 flush with the top thereof. The intermediate plate 2| is formed with a molding cavity 25 in which the major portion of the stem structure [0 is molded.

The socket member 24, which is in axial alignment with cavity 25, is formed with an axial recess 26 adapted to receive the threaded end portion of the valve tube l2, said recess being tapered or countersunk at its upper end, as at 2'1, to receive the flange !6 of the said valve tube. The large end of countersink 2? opens into a shallow cavity 28 in the socket member, said cavity being contiguous with and constituting a continuation of molding cavity 25.

In the manufacture of the improved valve stem, when the valve tube l2 is mounted in the mold its flange [6 seats itself in the large end of the countersink 27 of socket member 24, the said tube being held in upright position by the mandrel and registering pin 23 which extends into its axial bore from the upper end thereof. The arrangement is such that the plastic rubber composition in the molding cavity of the mold may flow about .and cover the peripheral surface of the tube flange l6, yet the latter will so nicely seat in the countersink 21 as to prevent the rubber from flowing past said flange, even though there may be small variations in the diameter of the flanges of the valve tubes.

The invention prevents the flow of rubber onto the threaded end of the valve tubes so that buffing thereof is not required, and it achieves the other advantages set out in the foregoing statement of objects.

Modification may be resorted to without departing from the spirit of the invention or the scope of the appended claim.

What is claimed is:

V The method of forming a valve stem consisting of rubber attached to a hollow metal member provided with a bearing surface, which comprises applying unvulcanized rubber to a predetermined portion of the metal member adjacent one end thereof and adjacent said bearing surface and preventing creeping of said rubber beyond said predetermined portion during curing in a mold by having the faces of the vulcanizing mold in engagement with the bearing surface on the metal member.

THARON J. ELLIS. 

